Once you’re aware of character type, you’ll find yourself noticing it more and more in what you read and watch. You can then use this awareness to study that character and see what elements you can use in your own writing.
The megalomaniacal CEO. The sociopathic killer. The suicidal teen. The anxious woman self-medicating with booze and pills while caring for her demented mother. As writers, we invite these characters into our stories because they are true-to-life and because their psychological problems invite curiosity and compassion.
I’ve heard many people describe their progression as a writer, and I’ve been surprised not by how different these stories are, but how similar. That doesn’t mean everyone goes through these specific steps or does it in exactly this order, just that these growth experiences are shared by a lot of people.